I used JRockIT for some stuff. We found it to beat HotSpot (at the time) in some of our use cases. Eventually they got brought in house and HotSpot gained tho

I used JRockIT for some stuff. We found it to beat HotSpot (at the time) in some of our use cases. Eventually they got brought in house and HotSpot gained those speed improvements. One of the things that was really useful with it was Mission Control, which didn't exist to the same degree with the HotSpot VM.